> For the complete documentation index, see [llms.txt](https://docs.e6data.com/query-engine/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.e6data.com/query-engine/guides/clusters/zero-downtime-upgrades.md).

# Zero-downtime upgrades

How e6data upgrades a cluster's version without interrupting queries, and how it recovers if the new version is unhealthy.

When you change a cluster's version, e6data upgrades it **without interrupting queries**.

## How it works

The new version is brought up **alongside** the running one. Once the new version is healthy, traffic switches over to it, and the old version **drains in-flight queries** before shutting down. Queries are never cut off - those already running finish on the version that started them, and new queries route to the new version once it's ready.

During the upgrade the cluster shows the **Updating** state; queries continue on the current version throughout.

## Automatic rollback

If the new version fails its health checks, e6data **automatically rolls back** to the previous version - you don't need to intervene. The cluster stays on the version that was working.

## Triggering an upgrade

Change the cluster's **Version** from its **Edit** screen. You select from a curated set of available releases; the e6data team manages which versions are published and tested. See [Create and manage clusters](/query-engine/guides/clusters/create-and-manage-clusters.md#manage-and-upgrade) and [Runtime versions](broken://pages/zRA16p6NBcnW3lYEWhr2).

{% hint style="info" %}
You can't change the version while a cluster is mid-deployment or in a failed state - wait for it to reach a steady state first.
{% endhint %}

## See also

* [Create and manage clusters](/query-engine/guides/clusters/create-and-manage-clusters.md)
* [Lifecycle states and error codes](/query-engine/guides/clusters/lifecycle-states-and-error-codes.md)
* [Upgrades and releases](/query-engine/guides/operations/upgrades-and-releases.md) - platform-wide version management.


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